Image processing apparatus and storage medium

ABSTRACT

An image processing apparatus includes a hardware processor. The hardware processor estimates a body thickness and an irradiation field region of a subject based on a radiograph obtained by radiographing the subject. Further, the hardware processor calculates a distance from a focus of a radiation source to a radiation entrance point based on the body thickness. Still further, the hardware processor calculates an irradiation field size based on the irradiation field region. Yet further, the hardware processor calculates an exposure dose based on the distance, the irradiation field size, and in imaging condition used in radiographing the subject.

CROSS-REFERENCE TO RELATED APPLICATIONS

The entire disclosure of Japanese Patent Application No. 2019-029110filed on Feb. 21, 2019 is incorporated herein by reference in itsentirety.

BACKGROUND Technological Field

The present disclosure relates to an image processing apparatus and astorage medium.

Description of the Related Art

An equation for estimating exposure doses of patients with whichexposure doses (entrance surface doses) of patients can be easilyobtained in any medical facility is disclosed in the followingliterature: Hiroki SHIMAZAKI and seven other persons, “Estimatedequation of Patient dose in Diagnostic radiology”, Japanese journal ofMedical Physics, vol. 19, no. 4, pp. 209-217. The equation forestimating exposure doses of patients has been made by adding acorrection factor to an approximate equation that expresses X-ray outputof X-ray apparatuses.

SUMMARY

However, the abovementioned equation for estimating exposure doses ofpatients uses fixed values as values of the body thickness and theirradiation field size that are necessary for determining a backscatterfactor. Hence, accuracy of exposure doses of patients calculated by theabove equation is low.

The present invention has been conceived in view of the above problems,and objects thereof include providing an image processing apparatus anda storage medium for easily and accurately calculating exposure doses ofsubjects.

In order to achieve at least one of the abovementioned objects,according to a first aspect of the present invention, there is providedan image processing apparatus including a hardware processor that:

estimates a body thickness and an irradiation field region of a subjectbased on a radiograph obtained by radiographing the subject;

calculates a distance from a focus of a radiation source to a radiationentrance point based on the estimated body thickness;

calculates an irradiation field size based on the estimated irradiationfield region; and

calculates an exposure dose based on the calculated distance, thecalculated irradiation field size, and an imaging condition used inradiographing the subject,

According to a second aspect of the present invention, there is provideda non-transitory computer-readable storage medium storing a program thatcauses a computer to:

estimate a body thickness and an irradiation field region of a subjectbased on a radiograph obtained by radiographing the subject;

calculate a distance from a focus of a radiation source to a radiationentrance point based on the estimated body thickness;

calculate an irradiation field size based on the estimated irradiationfield region; and

calculate an exposure dose based on the calculated distance, thecalculated irradiation field size, and an imaging condition used inradiographing the subject.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, advantages, and features provided by one or moreembodiments of the present invention will become more fully understoodfrom the detailed description given hereinbelow and the appendeddrawings that are given by way of illustration only, and thus are notintended as a definition of the limits of the present invention,wherein:

FIG. 1 is a block diagram showing configuration of a radiographicimaging system according to an embodiment(s);

FIG. 2 is a block diagram showing configuration of a radiographicimaging apparatus included in the radiographic imaging system shown inFIG. 1;

FIG. 3 is a block diagram showing configuration of a console included inthe radiographic imaging system shown in FIG. 1; and

FIG. 4 is a flowchart of an exposure dose calculation process that isperformed by the console shown in FIG. 3.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail with reference to FIG. 1 to FIG. 4. However, the scope of thepresent invention is not limited to the following embodiments, and it isneedless to say that the present invention can be appropriately modifiedwithin the scope of the present invention.

Although detailed description of subjects to be photographed is omitted,the present invention can be used to photograph any part of human body.In addition, the subjects are not limited to people but include animals.

[Radiographic Imaging System]

First, configuration of a radiographic imaging system according to anembodiment(s) will be described. FIG. 1 is a block diagram showingconfiguration of a radiographic imaging system 100.

As shown in FIG. 1, the radiographic imaging system 100 of thisembodiment includes an irradiation apparatus 1, a radiographic imagingapparatus 2, and a console 3 that functions as an image processingapparatus.

The radiographic imaging system 100 can be connected to a radiologyinformation system (RIS), a picture archiving and communication system(PACS), and so forth (all not shown).

The irradiation apparatus 1 can be communicably connected to the console3 by wire or wirelessly.

The irradiation apparatus 1 includes a generator 11, an exposure switch12, and a radiation source 13.

The generator 11 applies a voltage in accordance with preset imagingconditions (tube voltage, tube current, irradiation time (mAs value),etc.) to the radiation source 13 in response to the exposure switch 12being operated. Further, the generator 11 can send, to the console 3,imaging condition information indicating the imaging conditions used inradiographing a subject.

The radiation source 13 (light bulb) includes a rotating anode and afilament (both not shown). When the generator 11 applies the voltage tothe radiation source 13, the filament emits an electron beamcorresponding to the applied voltage to the rotating anode, and therotating anode generates radiation X (X-rays, etc.) of a dosecorresponding to the intensity of the electron beam.

Although FIG. 1 shows the components 11 to 13 that separate from oneanother, they may be unitized.

Further, although FIG. 1 shows the exposure switch 12 connected to thegenerator 11, the exposure switch 12 may be provided in/on anotherapparatus (e.g. a not-shown console).

The irradiation apparatus 1 may be installed in an imaging room, orcombined with a nursing cart or the like to be movable.

The radiographic imaging apparatus 2 is communicably connected to theconsole 3 by wire or wirelessly.

The radiographic imaging apparatus 2 generates image data of a subjectby receiving the radiation X via the subject from the irradiationapparatus 1.

The radiographic imaging apparatus 2 will be described in detail later.

The console 3 is constituted of a PC, a portable terminal, or adedicated apparatus, and is communicably connected to the irradiationapparatus 1, the radiographic imaging apparatus 2, and/or the like bywire or wirelessly.

The console 3 can set imaging conditions, an imaging target part(s)(part(s) of a subject to be photographed), and so forth into theirradiation apparatus 1 and the radiographic imaging apparatus 2 (viathe communication unit 32) on the basis of an imaging order from anexternal apparatus (RIS, etc.) or on the basis of user operations.

The console 3 will be described in detail later,

[Radiographic Imaging Apparatus]

Next, the radiographic imaging apparatus 2 included in the radiographicimaging system 100 will be described in detail. FIG. 2 is a blockdiagram showing configuration of the radiographic imaging apparatus 2.

As shown in FIG. 2, the radiographic imaging apparatus 2 includes acontroller 21, a radiation detector 22, a reader 23, a communicationunit 24, a storage 25, and a bus 26 that connects the components 21 to25 with one another.

The controller 21 includes a central processing unit (CPU) and a randomaccess memory (RAM), In response to control signals or the like receivedfrom external apparatuses, such as the console 3, the CPU of thecontroller 21 reads various programs stored in the storage 25, loads theread programs into the RAM, and performs various processes in accordancewith the loaded programs, thereby centrally controlling operation ofeach component of the radiographic imaging apparatus 2.

The radiation detector 22 is constituted of a substrate in which pixelsare arranged two-dimensionally (in a matrix), Each pixel has a radiationdetection element and a switch element. The radiation detection elementsgenerate charges corresponding to the dose of the radiation X received.

The reader 23 reads the amounts of charges discharged from therespective pixels as signal values, and generates image data from thesignal values.

The communication unit 24 receives various control signals, variousdata, and so forth from external apparatuses, and sends various controlsignals, generated image data, and so forth to external apparatuses.

The storage 25 includes a nonvolatile semiconductor memory and/or a harddisk, and stores various programs that are executed by the controller21, parameters that are required to perform processes in accordance withthe programs, and so forth. The storage 25 also stores image datagenerated by the reader 23 and various data processed by the controller21.

In the radiographic imaging apparatus 2 configured as described above,the radiation detector 22 accumulates, in the pixels, chargescorresponding to the dose of the radiation X by receiving the radiationX in a state in which the controller 21 has turned off the switchelements. When the controller 21 turns on the switch elements, and thecharges are discharged from the pixels accordingly, the reader 23converts the amounts of the charges into signal values, and reads thesignal values as image data.

The radiographic imaging apparatus 2 may be, what is called, an indirectradiographic imaging apparatus that includes a scintillator, andconverts received radiation X with the scintillator into light havinganother wavelength, such as visible light, and generates chargescorresponding to the light, into which the radiation X has beenconverted, or may be, what is called, a direct radiographic imagingapparatus that directly generates charges from received radiation Xwithout a scintillator or the like.

The radiographic imaging apparatus 2 may be integrated with an imagingtable (dedicated type), or may be portable (cassette type),

[Console]

Next, the console 3 included in the radiographic imaging system 100 willbe described in detail. FIG. 3 is a block diagram showing configurationof the console 3.

As shown in FIG. 3, the console 3 includes a controller 31 (hardwareprocessor), a communication unit 32, a storage 33, a display 34, anoperation unit 35, and a bus 36 that connects the components 31 to 35with one another.

The controller 31 includes a central processing unit (CPU) and a randomaccess memory (RAM). In response to operations on/with the operationunit 35, the CPU of the controller 31 reads various programs stored inthe storage 33, loads the read programs into the RAM, and performsvarious processes in accordance with the loaded programs, therebycentrally controlling operation of each component of the console 3.

The communication unit 32 includes a LAN adapter, a modem, and aterminal adapter (TA), and controls data sending to and data receivingfrom external apparatuses connected to a communication network(s).

The storage 33 includes a nonvolatile semiconductor memory and/or a harddisk, and stores various programs (including a program for an exposuredose calculation process described below) that are executed by thecontroller 31, parameters that are required to perform processes inaccordance with the programs, and so forth. The storage 33 also storesimage data received from the radiographic imaging apparatus 2 and imagedata processed by the controller 31.

The storage 33 also stores imaging condition information received fromthe irradiation apparatus 1. The storage 33 also stores alternative datato be used as imaging condition information when imaging conditioninformation is not received (obtained) from the irradiation apparatus 1in the exposure dose calculation process described below. Thealternative data are preset, and are pieces of information associatedwith respective predetermined imaging techniques in radiography.

The display 34 is constituted of a monitor, such as a liquid crystaldisplay (LCD) or a cathode ray tube (CRT), and displays instructionsinput from the operation unit 35, data, and so forth in accordance withinstructions of display signals input from the controller 31.

The operation unit 35 includes: a keyboard including cursor keys, numberinput keys, and various function keys; and a pointing device, such as amouse, and outputs, to the controller 31, instruction signals input by auser operating the keys of the keyboard or the mouse.

The operation unit 35 may have a touchscreen on the display screen ofthe display 34. In this case, the operation unit 35 outputs, to thecontroller 31, instruction signals input via the touchscreen.

[Exposure Dose Calculation Process]

Next, the exposure dose calculation process, which is one of theprocesses that are performed by the console 3, will be described indetail. FIG. 4 is a flowchart of the exposure dose calculation processthat is performed by the console 3.

The controller 31 of the console 3 of this embodiment performs theexposure dose calculation process in response to satisfaction of apredetermined start condition, such as a start operation on/with theoperation unit 35, a press on the exposure switch 12, or an imagingprocess with the irradiation apparatus 1 and the radiographic imagingapparatus 2. Examples of the exposure dose of a subject calculated inthe exposure dose calculation process include the dose area product, theentrance surface dose, the effective dose, and the equivalent dose.Methods for calculating the effective dose and the equivalent dose aredetailed in the following literature: Takashi MARUYAMA, Kazuo IWAI,Kanae, NISHIZAWA, Yutaka NODA and Yoshikazu KUMAMOTO, “Organ or TissueDoses, Effective Dose and Collective Effective Dose from X-RayDiagnostics, in Japan”, RADIOISOTOPES, vol. 45 (1996) no. 12.

As shown in FIG. 4, first, the controller 31 obtains image data(radiograph) generated by the radiographic imaging apparatus 2 inresponse to the irradiation apparatus 1 irradiating a subject withradiation (Step S1).

Preferably, the console 3 (controller 31) obtains the image data byreceiving the image data via the communication unit 32 by wire orwirelessly, but may obtain the image data via a medium, such as a USBmemory.

In order to obtain the image data, the console 3 may send a data sendingrequest signal to the radiographic imaging apparatus 2, therebyrequesting the radiographic imaging apparatus 2 to send the image data,or may wait (repeat Step S1) until the radiographic imaging apparatus 2sends the image data.

Next, the controller 31 performs a correction process(es), such as gaincorrection, offset correction, and/or defective pixel correction, on theimage data obtained in Step S1 (Step S2).

Next, the controller 31 determines whether or not it has obtainedimaging condition information indicating imaging conditions used inradiographing the subject from the irradiation apparatus 1 (generator11) (Step S3).

If the controller 31 determines in Step S3 that it has obtained imagingcondition information from the irradiation apparatus 1 (Step S3; YES),the controller 31 proceeds to Step S5.

If the controller 31 determines in Step S3 that it has not obtainedimaging condition information from the irradiation apparatus 1 (Step S3;NO), the controller 31 obtains (a piece of) alternative data from thestorage 33 as imaging condition information (Step S4) and proceeds toStep S5.

As described above, the alternative data are pieces of informationassociated with respective predetermined imaging techniques inradiography. The controller 31 obtains, as imaging conditioninformation, apiece of information associated with an imaging techniquespecified via the operation unit 35 among the pieces of informationassociated with the respective imaging techniques.

Next, the controller 31 estimates the body thickness on the basis of theimage data corrected in Step S2 and the imaging condition informationobtained in Step S3 or Step S4 (Step S5). As a method for estimating thebody thickness, for example, a method disclosed in JP 2016-067712 A maybe used. The controller 31 may estimate the body thickness on the basisof only the image data corrected in Step S2 without taking the imagingcondition information obtained in Step S4 into account. As a method forestimating the body thickness on the basis of only the image data, forexample, a method disclosed in JP 2015-167613 A may be used.

Next, the controller 31 calculates the distance from the focus of theradiation source 13 to a radiation entrance point (hereinafter, referredto as FSD (Focus (to) Surface Distance)) on the basis of the bodythickness estimated in Step S5 (Step S6). More specifically, thecontroller 31 calculates the FSD by subtracting the body thickness froma radiation-source-to-detector distance (hereinafter referred to as SID(Source to Image Distance)), which is included in the imaging conditioninformation.

Next, the controller 31 estimates the irradiation field region on thebasis of the image data corrected in Step S2 (Step S7). As a method forestimating the irradiation field region, for example, a method disclosedin JP 5,998,903 B may be used.

Next, the controller 31 calculates the irradiation field size (e.g. thelength of the irradiation field region in the horizontal direction andthe length of the irradiation field region in the vertical direction) onthe basis of the irradiation field region estimated in Step S7 (StepS8).

Next, the controller 31 calculates the exposure dose (entrance surfacedose and dose area product (DAP value) in this embodiment) on the basisof the FSD calculated in Step S6, the irradiation field size calculatedin Step S8, and the imaging conditions (kV, mAs, filter type) includedin the imaging condition information (Step S9). More specifically, thecontroller 31 calculates the entrance surface dose by substituting acorrection factor, which is determined by the FSD, the irradiation fieldsize, and the imaging conditions (kV, mAs, lifter type), into the NDDformula (simple surface dose conversion formula), and also calculatesthe dose area product (DAP value). As a method for calculating the dosearea product (DAP value), for example, a method disclosed in thefollowing literature may be used: Hajime SAKAMOTO and five otherpersons, “A Study of Patient's Dose Control Using an Area ExposureProduct Meter”, Japanese Journal of Radiological Technology, vol. 56,no. 10.

Next, the controller 31 sends data (exposure dose information) of theentrance surface dose and the dose area product calculated in Step S9 tothe radiology information system (RIS) (Step S10) and ends the exposuredose calculation process.

When sending the exposure dose information, the controller 31 may alsosend body thickness information indicating the body thickness estimatedin Step S5. This allows the radiology information system (RIS) to manageexposure doses of subjects (patients) by body type (e.g.slender/ectomorph, standard/mesomorph, plump/endomorph, etc.). As aresult, for example, the diagnostic reference levels (DRLs) can becalculated with only people of the standard body type targeted.

When sending the exposure dose information, the controller 31 may alsosend index information (e.g. EI value, S value, etc.) representing thequality of the radiograph. This allows the radiology information system(RIS) to identify values of exposure doses for the optimum quality ofradiographs.

When sending the exposure dose information, the controller 31 may alsosend failure/success information indicating whether or not theradiograph is a failed image. This allows the radiology informationsystem (RIS) to manage successful image data and failed image dataseparately from one another.

As described above, the controller 31 of the console 3 estimates thebody thickness and the irradiation field region of a subject on thebasis of image data (radiograph) obtained by radiographing the subject,calculates the distance (FSD) from the focus of a radiation source to aradiation entrance point on the basis of the estimated body thickness,calculates the irradiation field size on the basis of the estimatedirradiation field region, and calculates the exposure dose on the basisof the calculated FSD, the calculated irradiation field size, and animaging condition(s) used in radiographing the subject.

Thus, the exposure dose is calculated by using the FSD and theirradiation field size that are actually, calculated from the image data(radiograph). Hence, the exposure dose can be easily and accuratelycalculated.

Further, the controller 31 of the console 3 estimates the body thicknessby taking the imaging condition used in radiographing the subject intoaccount. Hence, an estimation error of the body thickness can bereduced.

Further, in response to not obtaining imaging condition informationindicating the imaging condition from the irradiation apparatus 1, thecontroller 31 obtains alternative data (preset information) as theimaging condition information. Thus, the exposure dose can be calculatedby using the alternative data.

Hence, even when the console 3 and the irradiation apparatus 1 are notin cooperation with one another, the exposure dose can be calculated.

Further, the alternative data includes pieces of information associatedwith respective predetermined imaging techniques in radiography, and thecontroller 31 of the console 3 obtains, as the imaging conditioninformation, a piece of the information associated with an imagingtechnique specified on the basis of a user operation. Hence, even whenthe console 3 and the irradiation apparatus 1 are not in cooperationwith one another, the exposure dose can be calculated accurately.

Those described in the above embodiment are preferred examples of thepresent invention, and hence not intended to limit the presentinvention.

For example, although in the above embodiment, both the entrance surfacedose and the dose area product (DAP value) are calculated as theexposure dose in the exposure dose calculation process, only one of theentrance surface dose and the dose area product (DAP value) may becalculated.

Further, for example, in the above embodiment, the irradiation apparatus1 may further include an area dosimeter (measurer), and the controller31 of the console 3 may determine whether or not a difference betweenthe exposure dose measured by the area dosimeter and the exposure dosecalculated in the above exposure dose calculation process is equal to orgreater than a predetermined threshold, and in response to determiningthat the difference is equal to or greater than the predeterminedthreshold, causes, for example, the display 34 (notifying unit) tonotify a user that the difference is equal to or greater than thepredetermined threshold.

Further, for example, in the above embodiment, the controller 31 of theconsole 3 may calculate the exposure dose on the basis of a signal valueof a hollow hole part of the radiograph (image data), determine whetheror not a difference between (i) the exposure dose calculated on thebasis of the signal value of the hollow hole part and (ii) the exposuredose calculated in the above exposure dose calculation process is equalto or greater than a predetermined threshold, and in response todetermining that the difference is equal to or greater than thepredetermined threshold, causes, for example, the display 34 to notify auser that the difference is equal to or greater than the predeterminedthreshold.

Further, for example, in the above embodiment, the controller 31 of theconsole 3 may specify the imaging condition information, which is usedin calculating the exposure dose in the above exposure dose calculationprocess, for example, via the operation unit 35. In this case, theimaging condition information can be corrected, for example, after theexposure dose is calculated, so that the exposure dose can berecalculated.

Further, for example, although in the above description, a hard disk anda nonvolatile semiconductor memory are disclosed as examples of acomputer-readable storage medium storing the program(s) of the presentinvention, the computer-readable storage medium is not limited to these.As the computer-readable storage medium, a portable storage medium, suchas a CD-ROM, may also be used. Also, as a medium that provides, via acommunication line, data of the programs) of the present invention, acarrier wave may be used.

The detailed configuration and detailed operation of each apparatus orthe like of the radiographic imaging system can also be appropriatelymodified within the scope of the present invention.

Although some embodiments of the present invention have been describedand illustrated in detail, the disclosed embodiments are made forpurposes of not limitation but illustration and example only. The scopeof the present invention should be interpreted by terms of the appendedclaims.

What is claimed is:
 1. An image processing apparatus comprising ahardware processor that: estimates a body thickness and an irradiationfield region of a subject based on a radiograph obtained byradiographing the subject; calculates a distance from a focus of aradiation source to a radiation entrance point based on the estimatedbody thickness; calculates an irradiation field size based on theestimated irradiation field region; and calculates an exposure dosebased on the calculated distance, the calculated irradiation field size,and an imaging condition used in radiographing the subject.
 2. The imageprocessing apparatus according to claim 1, wherein the hardwareprocessor estimates the body thickness by taking the imaging conditionused in radiographing the subject into account.
 3. The image processingapparatus according to claim 2, wherein the hardware processor obtainsimaging condition information indicating the imaging condition, and inresponse to not obtaining the imaging condition information, obtainspreset information as the imaging condition information.
 4. The imageprocessing apparatus according to claim 3, wherein the presetinformation includes pieces of information associated with respectivepredetermined imaging techniques in radiography, and the hardwareprocessor obtains, as the imaging condition information, a piece of theinformation associated with an imaging technique specified based on auser operation.
 5. The image processing apparatus according to claim 3,wherein the hardware processor specifies the imaging conditioninformation based on a user operation.
 6. The image processing apparatusaccording to claim 1, wherein the exposure dose includes at least one ofa dose area product and an entrance surface dose.
 7. The imageprocessing apparatus according to claim 1, wherein the hardwareprocessor sends exposure dose information indicating the calculatedexposure dose to an external apparatus together with at least one ofbody thickness information indicating the estimated body thickness,predetermined index information representing a quality of theradiograph, and failure/success information indicating whether or notthe radiograph is a failed image.
 8. The image processing apparatusaccording to claim 1, further comprising: a measurer that measures theexposure dose; and a notifying unit, wherein the hardware processor:determines whether or not a difference between the measured exposuredose and the calculated exposure dose is equal to or greater than apredetermined threshold; and in response to determining that thedifference is equal to or greater than the predetermined threshold,causes the notifying unit to notify a user that the difference is equalto or greater than the predetermined threshold.
 9. The image processingapparatus according to claim 1, further comprising a notifying unit,wherein the hardware processor: calculates the exposure dose based on asignal value of a hallow hole part of the radiograph; determines whetheror not a difference between (i) the exposure dose calculated based onthe signal value of the hallow hole part and (ii) the exposure dosecalculated based on the distance, the irradiation field size, and theimaging condition is equal to or greater than a predetermined threshold;and in response to determining that the difference is equal to orgreater than the predetermined threshold, causes the notifying unit tonotify a user that the difference is equal to or greater than thepredetermined threshold.
 10. A non-transitory computer-readable storagemedium storing a program that causes a computer to: estimate a bodythickness and an irradiation field region of a subject based on aradiograph obtained by radiographing the subject; calculate a distancefrom a focus of a radiation source to a radiation entrance point basedon the estimated body thickness; calculate an irradiation field sizebased on the estimated irradiation field region; and calculate anexposure dose based on the calculated distance, the calculatedirradiation field size, and an imaging condition used in radiographingthe subject.